The present invention relates to a semiconductor device and a manufacturing method thereof, and particularly to a technology which is effective when applied to a semiconductor device including a MISFET having a high-dielectric-constant gate insulating film and a metal gate electrode and to a manufacturing method thereof.
By forming a gate insulating film over a semiconductor substrate, forming a gate electrode over the gate insulating film, and forming source/drain regions by ion implantation or the like, a MISFET (Metal Insulator Semiconductor Field Effect Transistor) can be formed. For the gate electrode, a polysilicon film is typically used.
However, in recent years, as a MISFET element has been scaled down, a gate insulating film has been increasingly thinned, and the influence of the depletion of a gate electrode when a polysilicon film is used for the gate electrode cannot be ignored any longer. Accordingly, there is a technique which uses a metal gate electrode as the gate electrode to suppress the phenomenon of depletion of the gate electrode.
When the gate insulating film is increasingly thinned as a result of the scaling down of a MISFET element and a thin silicon oxide film is used as the gate insulating film, between the channel portion of the MISFET and the gate electrode thereof, electrons and holes tunnel through a barrier formed by the silicon oxide film. As a result, a so-called tunnel current is produced to undesirably increase a gate leakage current. Accordingly, there is a technique which uses a material (high-dielectric-constant film) having a dielectric constant higher than that of the silicon oxide film to increase the physical film thickness and thereby reduce a leakage current despite the same capacitance.
Japanese Unexamined Patent Publication No. 2010-287752 (Patent Document 1) discloses a technique which uses a hafnium-containing material for a High-k film.